As one of medical devices, a soft contact lens (a soft ophthalmic lens) is exemplified. In a commercially available soft contact lens, a hydrogel material having a water content of about 25% to about 80% is usually used. A water-containing soft contact lens made of a hydrogel material, however, causes a phenomenon that water evaporates from the contact lens because the contact lens contains water. By this phenomenon, certain percentage of contact lens wearers may feel dryness stronger than when the wearers are naked eye and may feel uncomfortable. Some wearers who complain of symptoms called contact lens dry eye have existed. In addition, a water-containing soft contact lens made of a hydrogel material is easily contaminated with components in a lacrimal fluid and contains large amount of water, and therefore, the lens also has a risk of bacterial proliferation. Moreover, although a silicone hydrogel material, which is a hydrogel material further containing a silicone component, has high oxygen permeability, and lipid stains easily adhere to the surface because the silicone component is hydrophobic. A problem that the lipid stain adhesion is not completely improved therefore arises even if a hydrophilic polymer such as polyacrylic acid is coated.
On the other hand, as a low water content soft contact lenses having high oxygen permeability, for example, a silicone rubber lens obtained by a method in which a platinum catalyst is added to a mixture of a polydimethylsiloxane in which both molecular ends are blocked with vinylmethylsilyl groups and a methyl hydrogen polysiloxane and the mixture is heated and cured by the molding method is known (Patent Literature 1).
In addition, contact lens materials having high oxygen permeability mainly made of polysiloxane having a plurality of polymerizable functional groups are also described in Patent Literatures 2 to 6. Among these Patent Literatures, in Patent Literature 6, a contact lens material made of a polymer obtained by polymerizing only bifunctional organic siloxane macromers or copolymerizing the macromers with other monomers is disclosed. As the monomer used for the copolymerization, an acrylic acid fluoroalkyl ester or a methacrylic acid fluoroalkyl ester and an acrylic acid alkyl ester or a methacrylic acid alkyl ester are disclosed.
However, in a conventional low water content soft contact lenses having high oxygen permeability, the following problems are also observed. The silicone rubber lens described in Patent Literature 1 has disadvantages that a hydrophilic treatment layer that is provided for improving a hydrophobic property of a lens surface is peeled and that fixation to a cornea occurs because of too large elasticity, and thus, has not been widely used in practical use.
The materials mainly made of a polysiloxane having a plurality of polymerizable functional groups described in Patent Literatures 2 to 6 have high oxygen permeability as well as flexibility, and therefore, the materials are considered as one of the materials suitable for a contact lens. However, the materials may cause fixation to a cornea because tackiness remains on the lens surface after polymerization and the lens has insufficient balance between flexibility and mechanical properties such as folding resistance.
Various methods have been known with respect to a method for modifying a surface of a medical device. Among them, methods of coating two or more polymer materials layer by layer and stacking the layers have been known (Patent Literatures 7 to 9). Among these methods, a method of alternately coating polymer materials having two opposite charges layer by layer is called an LbL method. The layers of each material are considered to be bonded to other layers made of a different material in a noncovalent bonding manner. However, high oxygen permeability soft ophthalmic lenses in which usefulness of this method is clearly described are only lenses made of a silicone hydrogel material and usefulness to a low water content soft ophthalmic lens has not been known. In addition, a conventional LbL coating has been carried out for many layers such as about 4 layers to about 20 layers, and therefore, a production process may become longer and a production cost may be increased.